AI-generated practice questions — Science (086) (CBSE Class 10)

AI-generated practice questions for Science (086), with model answers. These are not previous-year board questions — they are model-generated for extra practice. 1000 question(s), grouped by chapter and skill.

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Chemistry · Chapter 1: Chemical Reactions and Equations (140)

• Which of the following observations does NOT indicate that a chemical reaction has taken place? (A) Change in…
• When a magnesium ribbon is burned in air, it produces a white powder. What is this powder, and what two subst…
• Why is it necessary to balance a chemical equation?
• What is the difference between a skeletal chemical equation and a balanced chemical equation?
• What law of nature makes it necessary to balance a chemical equation?
• A student writes the equation: Mg + O₂ → MgO. Is this a complete and balanced chemical equation? State two wa…
• While balancing a chemical equation, a student writes H₂O₄ instead of 4H₂O to increase the number of oxygen a…
• Iron nails are dipped in copper sulphate solution. After some time, the blue colour of the solution fades. (i…
• What is a combination reaction? Give one example from everyday life where two substances combine to form a si…
• Calcium oxide reacts with water to form calcium hydroxide. What type of energy change occurs in this reaction…
• When lead nitrate is heated strongly, brown fumes are produced along with a solid residue and oxygen gas. (i)…
• Decomposition reactions can be brought about by different forms of energy. Name the three forms of energy tha…
• Iron nails are dipped in copper sulphate solution and left for some time. Name the type of chemical reaction…
• When sodium sulphate solution is mixed with barium chloride solution, a white precipitate of barium sulphate…
• In the reaction between copper(II) oxide and hydrogen gas, copper(II) oxide is converted to copper. Is copper…
• Why do chips manufacturers flush bags of chips with nitrogen gas before sealing them?
• Which of the following is NOT a reliable indicator that a chemical reaction has taken place? (A) Change in co…
• When a magnesium ribbon is burned in air, a new substance is formed. (i) Name the substance formed. (ii) Is t…
• Why is it necessary to balance a chemical equation?
• Mg + O₂ → MgO is written using correct chemical formulae, yet it is not accepted as a complete chemical equat…
• What law of nature makes it necessary to balance a chemical equation?
• Iron reacts with oxygen to form iron oxide. A student writes: Fe + O₂ → Fe₂O₃. What term is used to describe…
• While balancing a chemical equation, why is it not allowed to change the formula of a compound — for example,…
• Balance the following chemical equation: Mg + O₂ → MgO Write the balanced equation and state the ratio in whi…
• In a balanced chemical equation, state symbols are used alongside the formulae of substances. What do the sym…
• A student writes the following equation for the reaction between iron and steam: Fe + H₂O → Fe₃O₄ + H₂ (a) Ex…
• Iron nails are immersed in copper sulphate solution. After some time, the blue colour of the solution begins…
• When calcium oxide is added to water, is heat released or absorbed? What type of reaction (in terms of energy…
• Burning of coal can be represented as C + O₂ → CO₂, and hydrogen reacting with oxygen produces water (2H₂ + O…
• When lead nitrate is heated strongly, brown fumes are produced along with a solid residue and oxygen gas. Wha…
• Decomposition reactions can be driven by different forms of energy. Name the forms of energy that can cause d…
• White silver chloride turns grey when left in sunlight. What type of reaction is this, and what products are…
• Decomposition reactions are described as endothermic. What does the term 'endothermic' mean? Explain why deco…
• When iron nails are dipped in copper sulphate solution, the blue colour of the solution gradually fades. What…
• When sodium sulphate solution is mixed with barium chloride solution, an insoluble white solid settles at the…
• When copper(II) oxide reacts with hydrogen gas, copper and water are formed. Which substance is oxidised and…
• A substance gains oxygen during a chemical reaction. Is it oxidised or reduced?
• Chips manufacturers flush packets with nitrogen gas before sealing them. What problem does this prevent, and…
• Which of the following is NOT a reliable indicator that a chemical reaction has taken place? (A) Change in co…
• When a magnesium ribbon is burnt in air, a white powdery product is formed. Name this product and write the c…
• The burning of magnesium in air is represented as: Mg + O₂ → MgO. Is this a balanced chemical equation? Give…
• The skeletal chemical equation for magnesium burning in oxygen is written as: Mg + O₂ → MgO. Is this equation…
• What law of chemistry makes it necessary to balance a chemical equation?
• What is a skeletal chemical equation?
• When balancing a chemical equation, why is it not allowed to change the subscripts in a chemical formula?
• What do the notations (s), (l), (g) and (aq) represent when written alongside chemical formulae in an equatio…
• Water is commonly found as a liquid, but in some chemical reactions it is written as H₂O(g) in the equation.…
• What does it mean for a chemical equation to be 'balanced'? Using a simple example, describe how you would us…
• Iron nails placed in copper sulphate solution turn brownish after some time. What type of chemical reaction i…
• When calcium oxide is added to water, the resulting mixture feels hot to the touch. What does this tell you a…
• Freshly whitewashed walls initially have a dull finish, but after two to three days they develop a shiny appe…
• When ferrous sulphate crystals are heated, what change in colour occurs and what products are formed?
• Name the three types of decomposition reactions based on the energy used to bring them about, and give one ex…
• Why are decomposition reactions described as endothermic reactions?
• When lead nitrate is heated, brown fumes are produced along with a solid residue and oxygen gas. (i) Identify…
• When an iron nail is dipped in copper sulphate solution, the blue colour of the solution fades and a brownish…
• When sodium sulphate solution is mixed with barium chloride solution, a white precipitate forms. What type of…
• When copper(II) oxide is heated with hydrogen gas, which substance is reduced? Give one reason based on gain…
• Chips manufacturers flush bags of chips with nitrogen gas before sealing them. What problem does this prevent…
• Iron left in a humid atmosphere develops a reddish-brown coating over days, while magnesium ribbon, when igni…
• When zinc granules are added to dilute sulphuric acid, bubbles are observed and the container becomes warm. W…
• A student argues: 'When we cook food, no new substance is formed — it just gets soft and changes texture, so…
• A student trying to balance the equation Fe + H₂O → Fe₃O₄ + H₂ changes the formula of water to H₂O₄ in order…
• When magnesium burns in oxygen, a student writes the chemical equation as: Mg + O₂ → MgO. Explain why this eq…
• A student writes the equation for the burning of magnesium as: Mg + O₂ → MgO. (i) Why is this called a skelet…
• During a chemical reaction, the total mass of reactants is found to equal the total mass of products. How doe…
• When balancing a chemical equation, why is it incorrect to change the subscripts inside a chemical formula (e…
• What information does the notation (aq) convey when written alongside a substance in a chemical equation, and…
• The balanced equation for the reaction of iron with steam is: 3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g). Why is th…
• In a chemical equation, conditions such as heat or a catalyst are written above or below the arrow rather tha…
• Consider the unbalanced equation: Al + Cl₂ → AlCl₃. Which of the following correctly balances it? (A) Al + Cl…
• Physical states are described as not always necessary in a chemical equation. However, in some reactions spec…
• Compare a word equation with a balanced chemical equation for the same reaction. What additional information…
• When iron nails are dipped in copper sulphate solution, certain changes are observed after some time. (i) Sta…
• Calcium oxide reacts with water to form calcium hydroxide. What type of reaction is this, and what experiment…
• After whitewashing a wall with slaked lime solution, the wall slowly develops a hard, shiny finish over two t…
• The burning of coal and the formation of water from hydrogen and oxygen are both classified under the same ca…
• A student claims that every combination reaction must also be an exothermic reaction. Is the student correct?…
• When magnesium ribbon burns in air, a single product is formed. Identify the product and explain how this rea…
• When ferrous sulphate crystals are heated strongly, three products are formed. What are they, and how can you…
• Which of the following correctly identifies both the energy input and the type of decomposition in the reacti…
• Using one balanced chemical equation each, illustrate how a combination reaction and a decomposition reaction…
• During the electrolysis of water, why is the volume of gas collected at one electrode exactly double that col…
• Silver chloride is stored in dark-coloured bottles in laboratories. Explain the chemical reason for this prec…
• A student heats lead nitrate powder in a test tube and observes brown fumes along with a colourless gas. Writ…
• The decomposition of calcium carbonate is carried out on a large industrial scale. (i) Write the balanced che…
• When iron nails are placed in copper sulphate solution, the blue colour of the solution gradually fades and t…
• Zinc displaces copper from copper sulphate solution, and lead displaces copper from copper chloride solution.…
• Consider the reaction: Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s). (i) Identify the type(s) of chemical reaction t…
• When sodium sulphate solution is mixed with barium chloride solution, a white precipitate forms and sodium ch…
• A student states: 'All precipitation reactions are double displacement reactions, but not all double displace…
• When copper oxide is heated with hydrogen gas, the black coating turns brown. In this reaction, identify whic…
• In the reaction ZnO + C → Zn + CO, identify the oxidising agent and the reducing agent. Explain your answer i…
• A student claims: 'In a redox reaction, it is possible for one substance to be oxidised without any other sub…
• Iron exposed to moist air develops a reddish-brown coating, while silver kept in air gradually turns black. (…
• Chips manufacturers flush their packets with nitrogen gas before sealing. Explain why this step is necessary,…
• Both rusting of iron and rancidity of food are caused by oxidation, yet we use very different methods to slow…
• Burning of magnesium in air and the thermal decomposition of calcium carbonate both involve a metal compound…
• When iron nails are placed in copper sulphate solution, the blue colour of the solution fades and a brown dep…
• Which of the following correctly pairs a reaction type with its energy relationship? (A) Decomposition of wat…
• A student observes two reactions: (i) zinc granules dissolve in dilute sulphuric acid, warming the test tube;…
• The decomposition of silver chloride in sunlight and the displacement of copper from copper sulphate solution…
• Both a precipitation reaction and a decomposition reaction can produce an insoluble solid as one of the produ…
• Consider the following sequence: calcium carbonate is heated strongly → the product (CaO) is mixed with water…
• When magnesium ribbon is burned in air, the product formed is: (A) Magnesium nitride (B) Magnesium hydroxide…
• The reaction CaO(s) + H₂O(l) → Ca(OH)₂(aq) + Heat is an example of: (A) Decomposition reaction (B) Displaceme…
• When lead nitrate powder is heated, the brown fumes produced are of: (A) Nitrogen monoxide (B) Nitrogen dioxi…
• Which of the following is a precipitation reaction? (A) CaO + H₂O → Ca(OH)₂ (B) 2Mg + O₂ → 2MgO (C) Na₂SO₄(aq…
• In the reaction ZnO + C → Zn + CO, carbon is: (A) Oxidised (B) Reduced (C) Neither oxidised nor reduced (D) B…
• The decomposition of silver chloride in sunlight is used in: (A) Manufacture of cement (B) Black and white ph…
• What is the correct balanced form of the skeletal equation: Fe + H₂O → Fe₃O₄ + H₂ ? (A) Fe + 4H₂O → Fe₃O₄ + 4…
• Respiration is classified as an exothermic reaction because: (A) It produces carbon dioxide as a waste produc…
• When iron nails are placed in copper sulphate solution, the blue colour of the solution gradually fades. Whic…
• The green coating that forms on copper objects exposed to moist air is an example of: (A) Rancidity (B) Reduc…
• Chips manufacturers flush bags of chips with nitrogen gas in order to: (A) Increase the crunchiness of chips…
• In the reaction: CuO(s) + H₂(g) → Cu(s) + H₂O(l), which substance is reduced? (A) H₂ (B) H₂O (C) Cu (D) CuO
• Which type of reaction is: 2AgCl(s) → 2Ag(s) + Cl₂(g) when exposed to sunlight? (A) Thermal decomposition (B)…
• In a balanced chemical equation, the notation '(aq)' written alongside a chemical formula indicates that the…
• Assertion (A): When ferrous sulphate crystals are heated, they first lose water and then decompose to give fe…
• Assertion (A): A chemical equation must be balanced to be used for stoichiometric calculations. Reason (R): A…
• Assertion (A): Rancidity in food can be slowed down by storing food in airtight containers. Reason (R): Airti…
• When copper powder is heated in air, its surface turns black. Write the chemical equation for this reaction a…
• Why does a magnesium ribbon need to be cleaned with sandpaper before it is burned in air?
• List any two observations that indicate that a chemical reaction has taken place when zinc granules are added…
• What is meant by a skeletal chemical equation? State the law that makes it necessary to balance such an equat…
• Calcium hydroxide solution is passed through excess carbon dioxide gas. Name the type of reaction that occurs…
• Identify the substance oxidised and the substance reduced in the following reaction: MnO₂ + 4HCl → MnCl₂ + 2H…
• What is corrosion? With reference to the rusting of iron, write the chemical formula of rust and explain the…
• With the help of one example each, distinguish between a displacement reaction and a double displacement reac…
• Balance the following chemical equations: (i) HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + H₂O (ii) NaOH + H₂SO₄ → Na₂SO₄ + H₂…
• Thermal decomposition of calcium carbonate is an important industrial reaction. Write the balanced chemical e…
• When a solution of lead(II) nitrate is mixed with a solution of potassium iodide, a yellow precipitate is for…
• Translate the following word equations into balanced chemical equations, adding state symbols wherever approp…
• Using the reaction ZnO + C → Zn + CO as an example, explain why oxidation and reduction are said to occur sim…
• What is a chemical reaction? Describe, with the help of an activity, how the evolution of a gas and a change…
• (a) What are exothermic and endothermic reactions? Give one example of each with a balanced chemical equation…
• (a) Define oxidation and reduction in terms of gain or loss of oxygen or hydrogen. Give one example of each.…
• Read the following and answer the questions that follow: During whitewashing, calcium oxide (quick lime) is f…
• Read the following and answer the questions that follow: A science teacher demonstrates an experiment where l…
• Read the following and answer the questions that follow: Rajan noticed that a new iron gate installed at his…

Chemistry · Chapter 2: Acids, Bases and Salts (82)

• What is the colour of litmus solution in a neutral (neither acidic nor basic) solution, and from which type o…
• When zinc granules are added to dilute sulphuric acid, a gas is produced. Name the gas and state how you woul…
• When sodium carbonate reacts with dilute hydrochloric acid, a gas is produced. Name the gas and state what ch…
• Which of the following correctly describes what happens when a base reacts with an acid? (A) A salt and hydro…
• Glucose and alcohol also contain hydrogen in their molecules, yet they are not considered acids. What must an…
• What ion is produced by bases when dissolved in water, and what term is used for bases that are soluble in wa…
• What does the pH scale measure, and what pH value represents a neutral solution?
• A solution has a pH of 3 and another has a pH of 11. Identify which solution is acidic and which is basic, an…
• Equal concentrations of hydrochloric acid (HCl) and acetic acid (CH₃COOH) are taken in separate beakers. How…
• What is the chemical name and chemical formula of baking soda?
• When electricity is passed through brine, three useful products are formed. Name the products and state at wh…
• Copper sulphate crystals are blue, but when strongly heated they turn white. What explains this colour change…
• A white powder hardens when mixed with water and is used in making casts for broken bones. (i) What is this s…
• Baking soda solution is added to beetroot extract used as an acid-base indicator. What colour change would yo…
• A student spills some soap solution on a yellow curry stain on a white cloth. The stain turns reddish-brown.…
• Both litmus and turmeric can distinguish between acidic and basic solutions, yet neither is used when the exa…
• When zinc granules are added to dilute sulphuric acid, a gas is evolved. What is this gas, and how would you…
• Curd and sour substances should not be stored in brass or copper vessels. Why?
• Zinc reacts with dilute sulphuric acid to produce hydrogen gas, and it also reacts with sodium hydroxide solu…
• When carbon dioxide gas is bubbled through lime water, a white precipitate forms. However, if excess carbon d…
• Copper oxide is a black solid. When it is added to dilute hydrochloric acid with stirring, the black solid di…
• Glucose and hydrochloric acid both contain hydrogen, yet only HCl is classified as an acid. When solutions of…
• Why does dry HCl gas not exhibit acidic properties, even though HCl is a well-known acid?
• Which of the following best explains why an aqueous solution of sodium hydroxide conducts electricity? (A) Na…
• A student adds excess sodium hydroxide solution to a fixed volume of hydrochloric acid. (a) Write the ionic e…
• Two solutions have pH values of 3 and 11 respectively. Compare their H⁺(aq) ion concentrations and explain wh…
• Equal concentrations of hydrochloric acid and acetic acid are tested with a universal indicator. Hydrochloric…
• Acid rain flows into a freshwater river. Describe the chemical change it causes in the river water and explai…
• A patient suffering from excess acid production in the stomach is given milk of magnesia. Explain why this tr…
• Tooth enamel is the hardest substance in the human body, yet it gets corroded after eating sugary food. Expla…
• Sodium chloride, potassium nitrate, copper sulphate and sodium acetate are all salts. What determines whether…
• In the chlor-alkali process, electrolysis of brine produces products at both electrodes. Name the products re…
• Bleaching powder is produced by passing chlorine gas over dry slaked lime. Would the same reaction work with…
• A baker accidentally uses washing soda instead of baking soda while making a cake. The cake turns out flat an…
• Which of the following best explains why Plaster of Paris must be stored in a moisture-proof container? (A) M…
• Blue copper sulphate crystals turn white when heated strongly, but regain their blue colour when a few drops…
• Sodium hydrogencarbonate (baking soda) is used both in fire extinguishers and as an antacid. Explain, with re…
• Starting from common salt (NaCl), outline the sequence of steps by which washing soda (Na₂CO₃·10H₂O) is obtai…
• [short_answer] In a soda-acid fire extinguisher, dilute sulphuric acid reacts with sodium hydrogencarbonate s…
• Which of the following substances will turn blue litmus red? (A) Sodium hydroxide solution (B) Baking soda so…
• When zinc granules are added to dilute sulphuric acid, the gas evolved is: (A) Oxygen (B) Sulphur dioxide (C)…
• Dry HCl gas does not change the colour of dry litmus paper because: (A) HCl is a weak acid (B) HCl does not i…
• The process of electrolysis of brine produces three useful products. Which of the following is NOT one of the…
• Tooth enamel begins to corrode when the pH of the mouth falls below: (A) 7.0 (B) 6.0 (C) 5.5 (D) 4.5
• Which of the following is the correct chemical formula of Plaster of Paris? (A) CaSO₄ (B) CaSO₄.½H₂O (C) CaSO…
• When carbon dioxide gas is passed in excess through lime water, the white precipitate of calcium carbonate: (…
• Salts of a strong acid and a weak base have a pH: (A) Equal to 7 (B) Greater than 7 (C) Less than 7 (D) Equal…
• Baking powder used in cooking is a mixture of baking soda and: (A) Washing soda (B) A mild edible acid such a…
• Among the following, which is an olfactory indicator? (A) Litmus (B) Phenolphthalein (C) Onion (D) Methyl ora…
• A base that is soluble in water is specifically called: (A) A salt (B) An acid (C) An alkali (D) An indicator
• Reaction of zinc with sodium hydroxide solution produces hydrogen gas and: (A) Zinc chloride (B) Zinc oxide (…
• Assertion (A): When an aqueous solution of an acid is diluted, its pH value increases. Reason (R): Dilution d…
• Assertion (A): Metallic oxides are called basic oxides. Reason (R): Metallic oxides react with acids to form…
• Assertion (A): Plaster of Paris should always be stored in a moisture-proof container. Reason (R): Plaster of…
• Assertion (A): Non-metallic oxides are acidic in nature. Reason (R): Carbon dioxide reacts with sodium hydrox…
• Glucose and alcohol both contain hydrogen atoms but are not considered acids. What experimental evidence woul…
• A farmer finds that the crop yield in his field is poor and suspects soil acidity is the problem. Name two su…
• State what is meant by 'water of crystallisation'. Give one example of a salt that contains water of crystall…
• A bee sting causes an acidic reaction on the skin. What type of substance should be applied to relieve the pa…
• What is acid rain? State the pH value below which rain is classified as acid rain and explain one harmful eff…
• Sodium hydrogencarbonate (NaHCO₃) is used as an antacid and also as an ingredient in baking powder. Write the…
• Equal concentrations of hydrochloric acid (HCl) and acetic acid (CH₃COOH) are taken. Which of the two is a st…
• Describe how bleaching powder is manufactured from chlorine. Write the balanced chemical equation for this re…
• What happens when sodium carbonate (Na₂CO₃) reacts with dilute hydrochloric acid? Write the balanced equation…
• Our stomach produces hydrochloric acid to help in digestion. (a) What happens during indigestion? (b) What ty…
• Write the balanced chemical equation for the chlor-alkali process. Name the electrode at which (i) chlorine i…
• Fresh milk has a pH of about 6. As the milk turns to curd, does the pH increase or decrease? Explain why. A m…
• Two solutions X and Y are tested with universal indicator. Solution X shows a pH of 2 and solution Y shows a…
• (a) With a suitable example, explain what is meant by a neutralisation reaction. Write the ionic equation tha…
• (a) What is the pH scale? Explain how pH is related to the concentration of H⁺(aq) ions in a solution. How do…
• (a) Common salt (sodium chloride) is described as a raw material for several important chemicals. Starting fr…
• Read the following and answer the questions: Rahul and Priya are performing an experiment in the school labor…
• Read the following and answer the questions: During a science fair, students set up a display about the impor…
• Read the following and answer the questions: A chemistry teacher demonstrates two reactions to the class. In…
• Zinc reacts with both dilute sulphuric acid and sodium hydroxide solution to produce hydrogen gas, yet these…
• Dry HCl gas does not change the colour of dry litmus paper, but when HCl dissolves in water it turns blue lit…
• A farmer notices that his crops are growing poorly. He tests the soil and finds its pH is around 4. He treats…
• Assertion (A): When excess carbon dioxide is bubbled through lime water that has already turned milky, the wh…
• Baking soda and washing soda are both manufactured starting from sodium chloride, yet they serve very differe…
• Two students dissolve equal moles of HCl and CH₃COOH separately in water and measure the pH. Student A finds…
• Tooth enamel begins to corrode when the pH of the mouth falls below 5.5 after a meal. (i) Identify the substa…
• Copper sulphate crystals are blue but turn white on strong heating, and white Plaster of Paris sets hard when…

Chemistry · Chapter 3: Metals and Non-metals (77)

• Name two physical properties that are generally used to distinguish metals from non-metals.
• Which of the following is a physical property generally associated with metals? (A) They form acidic oxides w…
• When sodium reacts with cold water, name the two products formed.
• Potassium and sodium catch fire when they react with cold water, whereas calcium does not, even though all th…
• Which of the following correctly describes what happens when dilute hydrochloric acid is added to copper? (A)…
• Why is hydrogen gas not produced when most metals react with nitric acid, even though it is produced when the…
• Iron filings are added to copper sulphate solution and copper pieces are added to iron sulphate solution. Sta…
• Sodium reacts with chlorine to form sodium chloride. (i) What are the charges on the sodium and chloride ions…
• Ionic compounds do not conduct electricity in the solid state but conduct electricity when they are melted or…
• What is the difference between a mineral and an ore?
• Why cannot highly reactive metals like sodium and aluminium be extracted by heating their oxides with carbon?…
• (i) Why must sulphide and carbonate ores be converted into their oxides before reduction with carbon? (ii) Na…
• Graphite, a form of carbon, conducts electricity like a metal, whereas sulfur — also a non-metal — is a britt…
• Iodine is a non-metal, yet it has a shiny surface, and graphite is a non-metal that conducts electricity. Wha…
• A metal worker shapes copper into various forms for industrial use — flattening it into thin sheets and stret…
• Electric wires used in homes are made of copper or aluminium but are always covered with PVC or a rubber-like…
• Which of the following statements about the physical properties of metals is INCORRECT? (A) Mercury is the on…
• Sodium and potassium react violently with cold water, while calcium's reaction is comparatively less vigorous…
• When iron reacts with steam, the product is Fe₃O₄, not Fe₂O₃. Write the balanced chemical equation for this r…
• Which of the following correctly explains why hydrogen gas is NOT produced when copper reacts with dilute hyd…
• A student adds a piece of zinc to copper sulphate solution and observes that the blue colour of the solution…
• Aluminium oxide reacts with both hydrochloric acid and sodium hydroxide solution. Write the chemical equation…
• Hydrogen gas is not evolved when most metals react with nitric acid, yet it IS evolved when magnesium reacts…
• Metal X displaces metal Y from Y's sulphate solution, but metal Y cannot displace metal Z from Z's sulphate s…
• During the burning of metals in air, iron filings burn vigorously when sprinkled into a flame, yet a solid pi…
• Using electronic configurations, explain why magnesium chloride has the formula MgCl₂ while sodium chloride h…
• An ionic compound dissolves readily in water but does not conduct electricity in the solid state. However, wh…
• Which of the following statements correctly explains why ionic compounds have high melting points? (A) The mo…
• A student claims that since aluminium (atomic number 13) is a reactive metal, it should form an ionic compoun…
• Gold and silver are found in nature as free elements, while metals like sodium and calcium are never found in…
• [short_answer] Zinc sulphide (ZnS) and zinc carbonate (ZnCO₃) are two common ores of zinc. (i) Name the proce…
• Carbon (coke) is an effective reducing agent for extracting iron and zinc from their oxides, but it cannot be…
• [mcq] In the thermit reaction, iron(III) oxide is reduced to produce molten iron. Which of the following corr…
• In electrolytic refining of copper, explain what happens at each electrode during the process. Why do the ins…
• Iron nails are placed in three separate test tubes: one containing ordinary water open to air, one containing…
• Zinc is used to coat iron articles to protect them from rusting (galvanisation). Even if the zinc coating get…
• Pure iron is too soft and corrodes easily, so it is alloyed to make stainless steel. Which of the following c…
• Gold is preferred for making jewellery because it: (A) is the most malleable of all metals (B) does not react…
• When calcium reacts with cold water, a gas is evolved which makes the metal float on the surface. The gas evo…
• In electrolytic refining of copper, which component is used as the anode? (A) Pure copper strip (B) Impure co…
• Which of the following non-metals is a liquid at room temperature? (A) Sulphur (B) Iodine (C) Bromine (D) Pho…
• Aqua regia is a mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of: (A) 1…
• The process of converting a sulphide ore into its oxide by heating strongly in the presence of excess air is…
• Which of the following metals does NOT react with dilute hydrochloric acid? (A) Zinc (B) Iron (C) Copper (D)…
• An alloy of lead and tin is used for welding electrical wires. This alloy is known as: (A) Brass (B) Bronze (…
• Which of the following conditions is essential for iron to rust? (A) Presence of air alone (B) Presence of wa…
• Which of the following correctly represents the order of decreasing reactivity of metals? (A) Na > Ca > Mg >…
• Ionic compounds do not conduct electricity in the solid state, but do so in the molten state. What is the pri…
• A copper wire is placed in a solution of silver nitrate. After some time, a shiny deposit appears on the copp…
• Highly reactive metals such as sodium, magnesium and calcium are extracted by electrolysis of their molten ch…
• Assertion (A): Aluminium metal is highly reactive, yet it is widely used for making cooking utensils. Reason…
• Assertion (A): Hydrogen gas is not evolved when a metal reacts with dilute nitric acid. Reason (R): Nitric ac…
• Assertion (A): Ionic compounds generally have high melting and boiling points. Reason (R): A large amount of…
• Assertion (A): Carbon cannot be used to reduce sodium oxide or aluminium oxide to their respective metals. Re…
• Zinc oxide reacts with both dilute hydrochloric acid and with sodium hydroxide solution. Write the balanced c…
• Magnesium does not react with cold water but reacts with hot water and also with steam. What products are for…
• Define the term 'gangue'. Why is it necessary to remove gangue before extracting a metal from its ore?
• What is galvanisation? Why does a galvanised iron article remain protected against rusting even if its zinc c…
• State one physical property each that makes (i) iodine an exception among non-metals and (ii) graphite an exc…
• Distinguish between roasting and calcination. Give one example of each, with the relevant chemical equation.
• The thermit reaction is used to join railway tracks. Write the chemical equation for this reaction and explai…
• Four metals P, Q, R and S were tested with cold water, hot water and steam. P reacted vigorously with cold wa…
• Pure gold is described as 24 carat gold and is considered too soft for making jewellery. Explain why it is al…
• Explain why copper articles develop a green coating on their surface over time. Also explain the chemical nat…
• State any three general physical properties of ionic compounds. Explain why ionic compounds dissolve readily…
• (a) What is the reactivity series of metals? On the basis of the reactivity series, explain how metals are gr…
• (a) Describe the chemical properties of metals with respect to their reactions with (i) oxygen, (ii) water, a…
• (a) Compare the physical properties of metals and non-metals under the following heads: (i) physical state at…
• Read the following and answer the questions that follow: Ramesh is a jeweller who works with different metals…
• Read the following and answer the questions that follow: In a school laboratory, a teacher demonstrated the e…
• Read the following and answer the questions that follow: Preeti observed that when she added a clean iron nai…
• A student claims: 'Aluminium is highly reactive, so it should corrode rapidly in air and be useless for makin…
• Zinc can be extracted from zinc oxide by heating with carbon, but sodium cannot be extracted from sodium oxid…
• An alloy of copper and zinc does not conduct electricity as well as pure copper, even though both copper and…
• Trace the complete journey of zinc from its naturally occurring sulphide ore to a pure, usable metal. Your an…
• Both the formation of ionic compounds (e.g., NaCl from sodium and chlorine) and the extraction of highly reac…
• Non-metals and metals both react with oxygen, yet the oxides they form behave oppositely when dissolved in wa…

Chemistry · Chapter 4: Carbon and its Compounds (105)

• Carbon is found in very small amounts in the earth's crust and atmosphere, yet it is considered one of the mo…
• Carbon has an atomic number of 6. How many valence electrons does a carbon atom have, and what is its valency?
• Carbon has an atomic number of 6 and needs 4 more electrons to achieve a noble gas configuration. Why does ca…
• Carbon compounds generally have low melting and boiling points compared to ionic compounds. What does this te…
• Most carbon compounds are poor conductors of electricity. Explain why covalent bonding results in the absence…
• Consider the following statements about covalent compounds and select the one that is correct. (A) Covalent c…
• What is catenation? Why is carbon able to form long chains and rings with other carbon atoms, while silicon s…
• Which of the following pairs correctly distinguishes saturated from unsaturated carbon compounds? (A) Saturat…
• Methanol, ethanol, propanol, and butanol belong to the same homologous series. (i) What is the structural dif…
• Ethane (C₂H₆) and ethene (C₂H₄) are both compounds of carbon and hydrogen. Which one is saturated and which i…
• Which of the following statements correctly explains why unsaturated carbon compounds are more reactive than…
• Two compounds both have the molecular formula C₄H₁₀ but have different structures. What are such compounds ca…
• What is a functional group in a carbon compound? How does the functional group determine the chemical propert…
• When an organic compound is subjected to complete combustion in excess oxygen, name the products formed that…
• What is a homologous series? State two characteristics that all members of a homologous series share.
• Write the IUPAC name and structural formula of the simplest ketone that has three carbon atoms in its chain.
• Saturated hydrocarbons burn with a clean blue flame while unsaturated hydrocarbons burn with a sooty yellow f…
• When a saturated hydrocarbon burns in a limited supply of air, what kind of flame is produced and what deposi…
• Which of the following correctly describes why fuels such as coal and petroleum are considered environmental…
• A student burns two different hydrocarbons in air and observes that one produces a clean blue flame while the…
• Ethanol is converted to ethanoic acid using alkaline potassium permanganate. (i) What type of chemical reacti…
• What type of compound is formed when hydrogen is added to an unsaturated hydrocarbon? Name one catalyst used…
• Why does carbon form covalent bonds rather than losing or gaining electrons to form ions?
• Using the formation of a hydrogen molecule (H₂) as an example, explain how sharing a pair of electrons in a c…
• Which of the following correctly describes why covalent compounds generally have low melting and boiling poin…
• A student dips two electrodes into liquid ethanol and finds that no current flows, but when the same electrod…
• Oxygen forms a double bond in O₂, but hydrogen forms only a single bond in H₂. Using the concept of valence e…
• Nitrogen (N₂) forms a triple bond between its two atoms. State how many shared pairs of electrons are present…
• A student argues that a water molecule (H₂O) must contain double bonds because oxygen needs two more electron…
• In methane (CH₄), carbon forms four single bonds with four hydrogen atoms. A student suggests that carbon cou…
• In diamond, each carbon atom is bonded to four other carbon atoms in a three-dimensional structure, whereas i…
• Graphite conducts electricity, yet it is a non-metal made entirely of carbon atoms joined by covalent bonds.…
• Both carbon and silicon belong to Group 14 of the periodic table and have a valency of 4, yet carbon shows ex…
• The melting point of ethanol is 156 K and its boiling point is 351 K, while sodium chloride (an ionic compoun…
• If carbon were to form a C⁴⁺ ion by losing all four of its valence electrons, which shell would become its ou…
• A student claims that because N₂ has a triple bond and H₂ has a single bond, nitrogen gas should be three tim…
• Methane reacts with chlorine in the presence of sunlight to form chloromethane (CH₃Cl) and HCl. What type of…
• Ethanol reacts with sodium metal to release hydrogen gas. Based on this observation, what can you say about t…
• Carbon and silicon both belong to the same group of the periodic table, yet the number of known carbon compou…
• Ethyne (C₂H₂) decolourises bromine water while ethane (C₂H₆) does not. Based on the nature of bonding in each…
• Which of the following pairs are structural isomers of each other? (A) n-Butane (C₄H₁₀) and 2-methylpropane (…
• A student claims that CH₃OH, C₂H₅OH and C₃H₇OH belong to a homologous series. (i) State two pieces of evidenc…
• Cyclohexane (C₆H₁₂) and cyclohexene (C₆H₁₀) both have carbon atoms arranged in a ring, yet they show differen…
• When ethanol reacts with sodium metal, what are the two products formed?
• What is the role of concentrated sulphuric acid when ethanol is heated with it at a high temperature? Name th…
• Both ethanoic acid and hydrochloric acid are acids, yet they differ in strength. Explain why ethanoic acid is…
• When ethanoic acid reacts with ethanol in the presence of a few drops of concentrated sulphuric acid, a new c…
• Ethyne (C₂H₂) is described as an unsaturated compound, while ethane (C₂H₆) is saturated. What structural feat…
• A student is given two unlabelled compounds with molecular formulas C₃H₈ and C₃H₆. (i) Using the general form…
• What is a micelle? Describe how the structure of a micelle helps soap to clean oily dirt from clothes.
• Why does soap fail to produce a good lather and instead form a white curdy precipitate when used with hard wa…
• Two compounds, n-butane and isobutane, share the molecular formula C₄H₁₀. (i) Draw the structural formulae of…
• Hexane and cyclohexane both contain six carbon atoms. Write their molecular formulae and explain why the two…
• In an organic compound, all hydrogen atoms bonded to carbon are replaced one by one with chlorine atoms. (i)…
• Two organic compounds — one with the structure CH₃CH₂OH and another with the structure CH₃CH₂CH₂CH₂OH — both…
• Ethanol reacts with sodium metal to produce hydrogen gas. What is the other product of this reaction?
• Which of the following hydrocarbons decolourises bromine water and also undergoes hydrogenation in the presen…
• A carbon compound on reaction with alkaline potassium permanganate gets oxidised to form ethanoic acid. The o…
• Cyclohexane has the molecular formula C₆H₁₂. Which class of compounds does it belong to?
• Which of the following functional groups is present in propanal? ((A)) –OH ((B)) –COOH ((C)) –CHO ((D)) –CO–
• When soap is added to hard water, a white curdy precipitate is formed. What causes this?
• Heating ethanol at 443 K with excess concentrated sulphuric acid produces ethene. The role of concentrated su…
• In the reaction of methane with chlorine in the presence of sunlight, what type of bond in methane is broken…
• Why do covalent compounds generally not conduct electricity? ((A)) They have high melting points and therefor…
• Assertion (A): Saponification is the process used in the preparation of soap. Reason (R): When an ester is tr…
• Assertion (A): Carbon forms a very large number of compounds compared to any other element. Reason (R): Carbo…
• Assertion (A): Detergents are more effective than soaps in hard water. Reason (R): Unlike soap molecules, the…
• What is catenation? Why does carbon exhibit catenation to a much greater extent than silicon?
• State two characteristics of a homologous series. A compound belonging to the carboxylic acid series has the…
• Ethanoic acid reacts with sodium hydrogencarbonate. Write the balanced chemical equation for this reaction an…
• Why does graphite conduct electricity while diamond does not, even though both are allotropes of carbon?
• Name one oxidising agent that can convert ethanol to ethanoic acid. Explain, in terms of the change in the co…
• (i) Draw the electron dot structure of ethyne (C₂H₂). (ii) State whether ethyne is saturated or unsaturated,…
• Carbon cannot form C⁴⁺ or C⁴⁻ ions easily. Explain why, and describe how carbon instead achieves noble gas co…
• (i) Write the IUPAC names of the following compounds: (a) CH₃CH₂CH₂OH (b) CH₃CH₂Br (c) CH₃COCH₂CH₃ (ii) Which…
• Vegetable oils are hydrogenated industrially to produce vanaspati ghee. (i) Name the catalyst used. (ii) Writ…
• Give reasons for the following: (i) The melting and boiling points of covalent compounds are generally low. (…
• Draw the structural formulae of the two possible structural isomers of butane (C₄H₁₀) and write their common…
• (i) A substance 'X' has the molecular formula C₂H₅OH. (a) Write the IUPAC name of X. (b) Write the chemical e…
• (i) Explain in detail the cleansing action of soap. In your answer, include: (a) the structure of a soap mole…
• (i) Draw the structures of all possible structural isomers of pentane (C₅H₁₂). How many structural isomers ar…
• Read the following and answer the questions that follow: Rahim noticed that the bottom of his cooking vessel…
• Read the following and answer the questions that follow: Preeti carried out an experiment in the school labor…
• Read the following and answer the questions that follow: A chemistry teacher showed students two test tubes —…
• Two successive members of a homologous series always differ by a –CH₂– unit. What is the corresponding differ…
• Pentanol (C₅H₁₁OH) and methanol (CH₃OH) belong to the same homologous series but have very different boiling…
• A student argues: 'Butanol and ethanol belong to the same homologous series, so they must have identical boil…
• A carbon compound has three carbon atoms in its chain and contains a ketone functional group. What is its IUP…
• A student is given two compounds: 'butane' and 'but-1-yne'. (i) Draw their structural formulae and identify t…
• Ethyne (C₂H₂) is used as fuel in oxy-acetylene welding, where it is burnt with pure oxygen rather than air. (…
• A student burns two different hydrocarbons — one saturated and one unsaturated — and holds a metal plate abov…
• A gas stove flame that was previously blue has turned yellow and the bottom of the cooking vessel is getting…
• Combustion of ethanol is classified as an oxidation reaction. Give one reason to justify this classification.
• Ethyne (C₂H₂) is used as fuel in welding torches where it is burned with pure oxygen rather than air. Using y…
• Diamond, graphite, and fullerene are all allotropes of carbon. (i) Briefly describe the structural arrangemen…
• Ethanol is treated separately with (i) alkaline potassium permanganate and (ii) excess concentrated sulphuric…
• Vegetable oils and vanaspati ghee both contain long carbon chains, yet doctors advise against regular consump…
• Methane reacts with chlorine in sunlight to give chloromethane (CH₃Cl) and HCl, but the same reaction does no…
• When ethanol is heated with concentrated sulphuric acid at 443 K, ethene is produced. When the same ethanol i…
• When ethanol reacts with sodium metal, hydrogen gas is evolved. What does this observation tell you about the…
• Ethanol, when heated with concentrated sulphuric acid at 443 K, undergoes a chemical change. (i) What role do…
• Methanol and ethanol are both alcohols, yet ingesting methanol in very small amounts can be fatal while ethan…
• Industrial ethanol is often mixed with small amounts of poisonous substances such as methanol before being so…
• Ethanol is used as a solvent in many medicines such as tincture iodine, and it is also completely miscible wi…
• Ethanol reacts with ethanoic acid in the presence of a few drops of concentrated sulphuric acid on gentle hea…

Biology · Chapter 5: Life Processes (95)

• Even when an organism appears to be completely still, certain processes must keep going on inside its body. N…
• Why do living organisms need a continuous supply of energy even when they are not performing any visible acti…
• Bile juice does not contain any digestive enzymes, yet it plays a crucial role in the digestion of fats. Expl…
• Name the raw materials required for photosynthesis and the main product stored by the plant as an energy rese…
• Fungi such as bread moulds and mushrooms cannot take in solid food the way animals do. How do they obtain nut…
• What is the role of bile juice in the digestion of fats in the small intestine?
• Why does the small intestine of a herbivore tend to be longer than that of a carnivore?
• Describe how a protein in food is digested as it passes through the human alimentary canal. Name the organs a…
• Where in the cell does the first step of glucose breakdown occur, and what molecule is produced at the end of…
• Distinguish between aerobic and anaerobic respiration in terms of: (i) where each occurs in the cell, (ii) th…
• During intense physical exercise, muscle cells may temporarily switch from aerobic to anaerobic respiration.…
• Aquatic organisms breathe much faster than terrestrial organisms of comparable size. What is the biological r…
• A researcher observes a microscopic particle that shows no sign of any metabolic activity when isolated in a…
• What is the role of haemoglobin in the transport of oxygen in human beings?
• Why do arteries have thick, elastic walls while veins do not?
• Name the chambers of the heart that oxygenated blood passes through after returning from the lungs, before it…
• Which of the following correctly describes the function of lymph? ((A)) It carries oxygen from the lungs to b…
• How does water move from the soil into the root xylem, and what force drives its upward movement through the…
• A student argues: 'A seed sitting in a dry jar is not alive because it shows no visible movement and carries…
• Explain why nutrition occupies a central position among all life processes. How would the absence of nutritio…
• What is the basic filtration unit of the kidney? Name the tiny cup-shaped structure in which its capillary ne…
• Plants do not have kidneys, yet they are able to remove waste products from their bodies. Describe any two st…
• A student sets up two identical potted plants under bell jars sealed airtight to glass plates. A watch-glass…
• A variegated plant has green and white (non-green) regions on the same leaf. When such a leaf is tested for s…
• Desert plants such as cacti open their stomata only at night to absorb carbon dioxide, which is stored as an…
• Guard cells control whether stomatal pores are open or closed. On a hot, dry day a plant begins to wilt due t…
• A farmer notices that even after providing adequate water, sunlight, and carbon dioxide, his crop plants show…
• Fungi like bread moulds and mushrooms cannot engulf food particles the way Amoeba does, yet they successfully…
• Bread mould and Amoeba are both heterotrophs, yet they obtain nutrition in fundamentally different ways. Comp…
• The small intestine receives secretions from both the liver and the pancreas. What specific problem does each…
• A person's stomach lining produces insufficient mucus. Explain the consequence this would have, and why the s…
• Herbivores like cows have a much longer small intestine than carnivores like tigers. What is the functional r…
• The large intestine does not produce any digestive enzymes. Despite this, explain why it is considered an ess…
• A student argues: 'Since digestion is already complete in the small intestine, the specific structure of the…
• Glucose is a six-carbon molecule. When it is broken down during cellular respiration, the first step produces…
• A student says: 'Anaerobic respiration in yeast and anaerobic respiration in human muscle cells are the same…
• Both aerobic and anaerobic respiration begin with the same glucose molecule, yet aerobic respiration releases…
• After an intense sprint, a runner experiences painful cramps in the leg muscles. Explain the biochemical reas…
• A sealed jar contains a germinating seed respiring aerobically. After 24 hours the oxygen inside is almost us…
• During bright daylight, a student holds a lit candle near a healthy potted plant and notices the flame is not…
• Aquatic fish breathe much faster than terrestrial mammals of a similar body size. What is the underlying reas…
• Carbon dioxide and oxygen are both transported through the same blood vessels, yet by entirely different mech…
• Which of the following is the correct site for the breakdown of pyruvate in aerobic respiration? (A) Cytoplas…
• In the human digestive system, which sphincter muscle regulates the release of food from the stomach into the…
• Oxygen-rich blood returning from the lungs first enters which chamber of the human heart? (A) Right atrium (B…
• Which of the following correctly describes the role of bile in digestion? (A) It chemically digests proteins…
• Which of the following organisms performs anaerobic respiration and produces ethanol and carbon dioxide? (A)…
• In a fish, blood passes through the heart only once during each complete circulatory cycle. This type of circ…
• Lymph is similar to blood plasma but differs from it in one important way. Which of the following correctly s…
• Which of the following end products of digestion are produced from fats by the action of lipase? (A) Amino ac…
• Assertion (A): Aquatic animals breathe at a much faster rate compared to most terrestrial animals. Reason (R)…
• Assertion (A): In mammals and birds, the left and right sides of the heart are completely separated. Reason (…
• Assertion (A): Arteries have thicker and more elastic walls compared to veins. Reason (R): Blood flows throug…
• Assertion (A): Translocation of food in phloem can occur both upward and downward in a plant. Reason (R): Phl…
• Assertion (A): Desert plants take in carbon dioxide at night rather than during the day. Reason (R): Opening…
• State any two roles of hydrochloric acid secreted by the gastric glands in the stomach.
• Name two nitrogenous waste products excreted by the human kidneys. Why is it essential to remove them from th…
• Muscle cramps in athletes often occur during intense exercise. Explain the biochemical reason for this.
• Explain why the walls of the left ventricle are thicker than those of the right ventricle.
• State two ways in which plants store or dispose of waste products that are different from the method used by…
• Describe the role of villi in the small intestine. How does their structure make them well-suited to their fu…
• Trace the complete pathway of air from the nostrils to the alveoli in human beings, naming each structure the…
• What is transpiration? Explain how it helps in the movement of water and minerals from the roots to the leave…
• Compare aerobic and anaerobic respiration under the following heads: (i) requirement of oxygen, (ii) end prod…
• Explain how the length of the small intestine in herbivores and carnivores differs and why this difference ex…
• (a) State the location of haemoglobin in human blood and mention one structural feature that makes it suitabl…
• How does the process of translocation in phloem differ from the transport of water in xylem? Give two points…
• (a) Draw a labelled diagram of the human excretory system showing the kidneys, ureters, urinary bladder and u…
• With the help of a labelled diagram of the human heart, explain the mechanism of double circulation. Why is d…
• (a) List the three main events that occur during photosynthesis. (b) Explain the role of each of the followin…
• Read the following passage and answer the questions that follow. Rohan is a 45-year-old man who was recently…
• Read the following passage and answer the questions that follow. During a science fair, Priya set up two iden…
• Read the following passage and answer the questions that follow. Amit's grandfather was admitted to hospital…
• Deoxygenated blood returning from the body enters the right atrium of the heart. Why is it essential that thi…
• Arteries have thick, elastic walls while veins have thinner walls but contain valves. Explain why each of the…
• Why do birds and mammals need a completely four-chambered heart with fully separated oxygenated and deoxygena…
• In fish, blood passes through the heart only once during a single trip around the body. In humans, blood pass…
• Lymph is often described as 'returned tissue fluid.' (i) Explain how lymph is formed from blood plasma. (ii)…
• Plants have two separate conducting tissues — xylem and phloem — for transport. Why can the same tissue not b…
• During the day, transpiration pull is the major force driving water movement up the xylem, but at night, root…
• Translocation of food in phloem requires ATP energy, whereas the ascent of water through xylem does not direc…
• A patient is found to have a systolic blood pressure of 160 mm Hg and a diastolic pressure of 100 mm Hg. (i)…
• Compare the transport of water and minerals through xylem with the transport of food through phloem under the…
• The kidneys filter approximately 180 litres of blood plasma per day, yet the composition of urine is very dif…
• A patient's kidneys have failed and they are put on hemodialysis. The dialysing fluid used in the artificial…
• Which of the following correctly explains why plants do not need a specialised excretory organ like the kidne…
• Oxygen released during photosynthesis is described as a waste product of plants. Justify this statement, and…
• The initial filtrate produced in the kidneys of a healthy adult is about 180 litres per day, yet only 1–2 lit…
• Trace the journey of a single glucose molecule from its synthesis in a leaf cell to its use in releasing ener…
• Both the alveolus in the lungs and the nephron in the kidney perform filtration across thin-walled capillarie…
• A plant simultaneously performs photosynthesis, aerobic respiration and transpiration during a sunny afternoo…
• In human beings, the circulatory system acts as a link between the respiratory system and the excretory syste…
• Assertion (A): Mammals and birds maintain a complete separation between oxygenated and deoxygenated blood in…
• Both autotrophic plants and heterotrophic animals ultimately depend on ATP as their cellular energy currency,…
• A plant is placed in a well-lit but very dry environment, and its stomata close in response. Explain how this…

Biology · Chapter 6: Control and Coordination (99)

• Describe the journey of a nerve impulse from a receptor to an effector (muscle or gland). Name the types of n…
• Where in the nervous system is a reflex arc formed, and why is it located there rather than in the brain?
• When you accidentally touch a hot object, why is the response carried out without waiting for the brain to th…
• Name the part of the human brain that is responsible for thinking. List any two types of sensory information…
• Which one of the following correctly describes the role of the cerebellum? (A) It controls involuntary action…
• What two structures protect the brain and spinal cord in the human body?
• A plant bends towards sunlight over several hours, while a cat leaps away from a sudden loud noise in a fract…
• A buffalo continuously chews cud even when there is no new food in its mouth, while a child on a swing pumps…
• The leaves of a touch-me-not (chhui-mui) plant fold up and droop when touched. (i) Name the type of movement…
• The leaves of a sensitive plant (chhui-mui) fold up when touched at one point, even though the movement occur…
• When you accidentally step on a nail, the withdrawal of your foot happens before you consciously feel the pai…
• A student argues: 'Since reflex arcs evolved because the brain is too slow, animals with highly developed bra…
• [long_answer] You accidentally prick your finger with a pin. Trace the complete path of the nervous impulse —…
• What is meant by a tropic movement in plants? Give one example.
• A potted plant is kept near a window so that light falls on it from one side. After a few days, the shoot is…
• A tendril of a pea plant is touching a vertical stick on one side. Which side of the tendril will grow faster…
• Which of the following correctly describes geotropism in a germinating seed? (A) The root grows upward and th…
• When you accidentally touch a hot object, the withdrawal of your hand is completed before you consciously fee…
• A student argues: 'Reflex arcs are a primitive leftover — animals with complex brains don't really need them…
• You withdraw your hand from a hot object almost instantly, yet you feel the pain only a moment later. Using y…
• Both reflex actions and voluntary actions involve nerve impulses, yet they differ fundamentally in how they a…
• Which gland secretes adrenaline, and directly into which medium is this hormone released?
• State any three changes that occur in the human body when adrenaline is secreted during a frightening situati…
• A child is diagnosed with dwarfism caused by a hormone deficiency. Which hormone is deficient and which gland…
• Which of the following correctly describes the role of insulin in the body? (A) It is secreted by the pancrea…
• Explain how the feedback mechanism controls the secretion of insulin in the body. Use the example of blood su…
• A student argues that since reflex arcs already handle quick responses to danger, the brain's role in the ner…
• When you accidentally step on a nail, you not only pull your foot back instantly but also feel sharp pain a m…
• Which part of the brain is most directly involved when a gymnast maintains perfect balance while walking on a…
• The forebrain receives sensory impulses from the eyes, ears, nose, and skin simultaneously. Explain how the f…
• Classify the following actions as voluntary or involuntary, and for each involuntary action, name the specifi…
• A person suffers a stroke that selectively damages the mid-brain and hind-brain, leaving the forebrain comple…
• The brain is enclosed in a fluid-filled balloon inside a bony box, while the spinal cord runs through the ver…
• When a nerve impulse travels along a nerve fibre and reaches the point where the nerve meets a muscle, the el…
• A person suffers nerve damage that prevents electrical impulses from reaching the skeletal muscles of one leg…
• A gardener grows two identical seedlings in separate pots. Seedling A is placed near a window with light comi…
• The leaves of a sensitive plant (Mimosa) fold up when touched, even though the point of touch and the point o…
• When a pea plant tendril contacts a support, which part of the tendril grows more rapidly — the side touching…
• A gardener places a seedling near a window so that light comes from one side. After a few days, the shoot ben…
• The roots of a germinating seed always grow downward into the soil, while the shoot grows upward. Name the st…
• Which of the following correctly describes the role of auxin in phototropism? (A) Auxin is destroyed on the l…
• Explain why a plant root and a plant shoot respond in opposite directions to the same stimulus of gravity, an…
• Name ONE plant hormone that promotes cell division. State the type of plant tissue where it is found in great…
• A student claims: 'Tropic movements in plants are really the same as the movement of the leaves of a touch-me…
• Both gibberellins and abscisic acid are plant hormones with contrasting roles. Describe the role of each horm…
• Which of the following correctly describes the function of the cerebellum? (A) It controls involuntary action…
• When a nerve impulse reaches the end of an axon, what event allows it to continue to the next neuron?
• A squirrel encounters a predator. Which hormone prepares its body for 'fight or flight', and from which gland…
• Which of the following statements correctly identifies where reflex arcs are primarily located and why? (A) I…
• Which plant hormone inhibits growth, promotes seed dormancy, and causes stomatal closure during water stress?…
• Which of the following is NOT a function of thyroxin? (A) Regulation of carbohydrate, protein and fat metabol…
• The peripheral nervous system consists of: (A) The brain and the spinal cord (B) The cranial nerves and spina…
• When germinating bean seeds are placed so that only one side receives light, the shoots bend towards the ligh…
• A deficiency of growth hormone during childhood results in: (A) Gigantism — abnormally large body size (B) Dw…
• How do plant cells bring about movement in the absence of muscle tissue?
• Which of the following correctly pairs a hormone with the process it primarily controls? (A) Insulin — regula…
• Which region of the fore-brain is associated with the sensation of hunger?
• Which of the following correctly identifies the structural protection provided to the brain and spinal cord r…
• Assertion (A): Iodised salt is recommended in the human diet. Reason (R): Iodine is essential for the synthes…
• Assertion (A): Reflex actions are carried out without conscious thought. Reason (R): In a reflex action, the…
• Assertion (A): Plant hormones are synthesised at places away from where they act. Reason (R): Plant hormones…
• Assertion (A): The level of insulin secreted by the pancreas decreases when blood sugar levels fall. Reason (…
• Assertion (A): Electrical impulses are a faster means of communication in the body than chemical signals. Rea…
• Name the part of a neuron where information from the environment is first received. How is this information t…
• A patient is unable to maintain balance while walking and stumbles frequently, even though his leg muscles ar…
• Distinguish between voluntary and involuntary actions, giving one example of each. Which part of the brain co…
• Why is the movement of the leaves of a touch-me-not plant in response to touch considered different from the…
• State two physiological changes that occur in the body when adrenaline is released into the blood. Explain ho…
• Diabetes mellitus patients are treated with insulin injections rather than oral tablets. Suggest a reason why…
• What is geotropism? With the help of an example each, distinguish between positive geotropism and negative ge…
• Draw a neat labelled diagram of a neuron. Name any two parts shown in your diagram and state the specific fun…
• What happens at the synapse between two neurons? Why is it important that a synapse converts an electrical si…
• How does a pea plant tendril coil around a support? Name the type of movement involved and explain the mechan…
• Compare the manner in which the nervous system and the endocrine system achieve control and coordination in a…
• Explain how auxin causes a plant shoot to bend towards light. In your answer, describe (i) where auxin is pro…
• (i) Define a reflex arc. Draw a labelled diagram of a reflex arc and trace the complete sequence of events th…
• (i) Draw a neat labelled diagram of the human brain identifying its three major regions. (ii) Describe the sp…
• (i) Plants show two broad categories of movement — one that involves growth and one that does not. Explain ea…
• Read the following and answer the questions that follow: Rahul was studying late at night when he accidentall…
• Read the following and answer the questions that follow: Dr. Sharma is examining two patients. Patient A has…
• Read the following and answer the questions that follow: A biology teacher set up an experiment using freshly…
• A squirrel suddenly spots a predator. Which hormone prepares its body for 'fight or flight', and which gland…
• Adrenaline causes blood supply to the digestive system and skin to decrease while blood supply to skeletal mu…
• Both the nervous system and the endocrine system help animals respond to changes in the environment, yet the…
• A child's diet is consistently deficient in iodine over several years. What visible symptom might develop, an…
• A child who consumes adequate food still shows stunted physical and mental development. Investigations reveal…
• Deficiency of growth hormone during childhood leads to dwarfism, while its excess can cause gigantism. What d…
• Which of the following correctly pairs a hormone with its source gland and its primary function? (A) Insulin…
• A diabetic patient's pancreas produces very little insulin. Explain why this leads to harmful effects in the…
• The amount of insulin secreted by the pancreas changes automatically as blood sugar levels rise and fall. Wha…
• A student claims: 'Animals do not need hormones for controlling growth because, unlike plants, animals do not…
• Compare nervous coordination and hormonal coordination in animals. In your answer, address how they differ in…
• Both plants and animals use chemical signals for coordination, yet animals also possess a nervous system. Exp…
• When a student accidentally steps on a nail, she withdraws her foot instantly but feels the pain a moment lat…
• Assertion (A): A person with a damaged cerebellum can still respond to a sudden loud noise by blinking, but s…
• The movement of a touch-me-not leaf and the bending of a shoot towards light both involve cells changing shap…
• A mountaineer stranded in extreme cold notices his heart is racing, his digestion has slowed, and he is breat…
• A child is diagnosed with both iodine deficiency and a deficiency of growth hormone secreted by the pituitary…
• Both the nervous system and the endocrine system help animals respond to changes in their environment, yet th…

Biology · Chapter 7: How do Organisms Reproduce? (140)

• Why does a change in the DNA of a cell lead to a change in the body design of an organism?
• When variations arise in a new DNA copy during cell division, what are the two possible outcomes for the orga…
• Variation during reproduction is described as beneficial to a species but not necessarily to an individual or…
• Name the mode of asexual reproduction used by each of the following organisms and briefly describe how it wor…
• Binary fission in Leishmania always occurs along a specific orientation, whereas in Amoeba it can occur in an…
• What is fragmentation as a mode of reproduction? Name one organism that reproduces by this method.
• Why can fragmentation work as a method of reproduction in Spirogyra but not in more complex multicellular org…
• Organisms like Hydra and Planaria can regrow into complete individuals from cut pieces. What is this ability…
• In Hydra, where does a bud originate, and what happens to it once it is fully mature?
• Which of the following is NOT a feature of vegetative propagation in plants? (A) Offspring can bear flowers a…
• In Bryophyllum, new plants develop from the margins of its leaves. Which part of the plant does this illustra…
• DNA in the cell nucleus controls the production of proteins, and proteins determine body design. Using this c…
• Variations arising during reproduction are essential for species survival, yet the same variations could be h…
• What is the function of the thick walls surrounding spores in organisms like Rhizopus?
• Why must germ-cells contain only half the number of chromosomes found in normal body cells?
• Why does the sexual mode of reproduction generate more variation in a population compared to asexual reproduc…
• In sexual reproduction, each new generation would have twice the amount of DNA as the previous generation — u…
• Which of the following best explains why sexual reproduction is advantageous for the long-term survival of a…
• How does the structure of a male gamete (sperm) differ from that of a female gamete (egg/ovum)?
• Which part of the pistil receives the pollen grain during pollination?
• What is the difference between self-pollination and cross-pollination?
• After pollination occurs in a flower, what series of changes eventually leads to the formation of a seed and…
• Why are the testes located outside the abdominal cavity in the scrotum?
• Which of the following correctly describes the path a sperm travels after being produced, until it exits the…
• Where in the female reproductive system does fertilisation normally take place? What is the immediate outcome…
• What is the role of the placenta in the development of an embryo inside the uterus?
• Why does menstruation occur every month?
• Which of the following contraceptive methods works by preventing the release of eggs? (A) Copper-T (B) Condom…
• Puberty marks the beginning of sexual maturation in human beings. Describe two physical changes that occur sp…
• Why are the testes located outside the abdominal cavity in the scrotum rather than inside the body?
• Name the structures, in order, that an egg passes through after it is released from the ovary until it reache…
• What is the role of the placenta in the development of an embryo inside the mother's body?
• What is shed from the uterus during menstruation, and why does it occur?
• Asexual reproduction by budding occurs in which of the following organisms? (A) Planaria (B) Yeast (C) Plasmo…
• In Leishmania, binary fission occurs in a definite orientation. Which feature of the cell determines this ori…
• The male germ-cells (sperms) in humans are produced in the testes, which are located outside the abdominal ca…
• A contraceptive copper-T device is placed inside the uterus to prevent pregnancy. However, it does NOT protec…
• In tissue culture, cells from the growing tip of a plant are placed in an artificial medium where they first…
• Which of the following is an example of a bisexual (hermaphrodite) flower? (A) Papaya (B) Watermelon (C) Must…
• Spores of Rhizopus are covered by thick walls. What is the primary advantage of this thick covering? (A) It h…
• Oral contraceptive pills prevent pregnancy primarily by: (A) Creating a mechanical barrier to stop sperm reac…
• Menstruation occurs approximately every month. Which of the following correctly describes why the uterine lin…
• Assertion (A): Variations are essential for the long-term survival of a species. Reason (R): If all individua…
• Assertion (A): Regeneration in organisms such as Hydra and Planaria is not considered a primary mode of repro…
• Assertion (A): Plants raised by vegetative propagation bear flowers and fruits earlier than plants grown from…
• Assertion (A): In sexual reproduction, each new generation does not end up with twice the DNA content of the…
• Assertion (A): Reproduction is not essential for the survival of an individual organism. Reason (R): Processe…
• Distinguish between cross-pollination and self-pollination on the basis of: (i) the source of pollen, and (ii…
• Name the structures that produce spores in bread mould (Rhizopus). Why can these spores survive harsh conditi…
• What are the two functions of the ovaries in the human female reproductive system?
• Why do multicellular organisms with specialised tissues and organs need more complex methods of reproduction…
• Explain the role of DNA copying in reproduction. Why is it important that DNA copies are similar but allowabl…
• Describe the journey of a pollen grain from the anther to the formation of a zygote inside the ovule of a flo…
• Compare binary fission in Amoeba with multiple fission in Plasmodium. How are these two methods different in…
• What happens to the ovule, ovary, and the other floral parts (petals, sepals, stamens, style, stigma) after f…
• Explain why sexual reproduction generates more variation in offspring than asexual reproduction. Why is this…
• Describe the path taken by a sperm from the site of its formation until it meets the egg in the human female…
• Surgical contraception involves blocking either the vas deferens in males or the fallopian tubes in females.…
• (a) Distinguish between a male gamete and a female gamete in terms of size, motility, and food reserves. (b)…
• (a) Draw a neat labelled diagram of the longitudinal section of a flower, labelling any four reproductive par…
• (a) List the components of the human male reproductive system and state the function of each. (b) Testosteron…
• Read the following passage and answer the questions that follow: A biology student observes two different org…
• Read the following passage and answer the questions that follow: After a flower is successfully pollinated, a…
• Read the following passage and answer the questions that follow: During the development of an embryo inside t…
• How does a condom help in preventing sexually transmitted infections?
• Which of the following contraceptive methods works by preventing the release of eggs through hormonal changes…
• If the vas deferens in a male is surgically blocked, why will fertilisation not occur?
• A newly formed DNA copy contains an error in the sequence of its nucleotides. What are the two possible outco…
• Why must DNA copying always be accompanied by the creation of additional cellular apparatus during cell divis…
• A scientist argues that if DNA copying were made perfectly accurate, it would actually be harmful to species…
• In a population of organisms occupying a stable niche, which of the following best explains why some variatio…
• Variation arising from DNA copying errors is described as beneficial to the species but not necessarily to th…
• A population of frogs lives in a pond that remains cool throughout the year. Due to climate change, the pond'…
• Variation arising from DNA copying errors is beneficial for a species but can be harmful to an individual org…
• [mcq] A forest contains two populations of beetles — Population X, in which all individuals are identical, an…
• Spirogyra reproduces by fragmentation, while Rhizopus reproduces by spore formation. (a) What is the key adva…
• Amoeba divides in any plane, but Leishmania always divides along a fixed orientation relative to its whip-lik…
• Plasmodium, the parasite that causes malaria, does not reproduce by simply splitting into two inside the huma…
• Spirogyra reproduces by fragmentation, but a complex animal like a frog cannot. What is the fundamental diffe…
• Both fragmentation and regeneration can result in new individuals arising from parts of an existing organism.…
• Which of the following best explains why Spirogyra, a multicellular organism, can reproduce by fragmentation…
• Fragmentation is classified as a form of asexual reproduction. Using this as a starting point, analyse what t…
• Hydra and Planaria can regenerate into complete organisms from cut pieces, yet regeneration is not classified…
• Both budding in Hydra and regeneration in Planaria involve the proliferation and differentiation of cells to…
• A farmer wants to grow a variety of rose that produces exceptionally fragrant flowers. He knows that seeds fr…
• [mcq] Banana plants and seedless oranges do not produce viable seeds. What does this imply about how new plan…
• In Bryophyllum, new plants arise from buds along the margins of leaves, while in potato, new plants arise fro…
• A plant produced from seed takes several years to flower for the first time, while a plant of the same specie…
• [long_answer] Vegetative propagation is classified as a form of asexual reproduction in plants. Justify this…
• [short_answer] In tissue culture, new plants are regenerated from a few cells taken from the growing tip of a…
• Rhizopus reproduces by spore formation under unfavourable conditions. Explain how the structural features of…
• Spore formation is classified as asexual reproduction, just like budding and fragmentation. Yet spore formati…
• During sexual reproduction, germ-cells undergo meiosis so that they contain only half the number of chromosom…
• Why does combining DNA from two different individuals during sexual reproduction not simply double the amount…
• Asexual reproduction can produce new individuals perfectly well. What specific advantage does sexual reproduc…
• A student argues: 'If DNA-copying were made less accurate, sexual reproduction would be unnecessary because e…
• Sexual reproduction combines variations from two parents rather than creating new mutations. Which of the fol…
• Why are germ-cells in complex multicellular organisms produced by meiosis rather than by the same cell divisi…
• In simple organisms, the two fusing germ-cells may look identical, but in complex organisms one gamete is lar…
• In complex multicellular organisms, the female gamete is significantly larger than the male gamete. Give a bi…
• A flower has its stamens removed before its pollen matures. Which of the following outcomes is most likely? (…
• After pollen lands on the stigma, it cannot directly fuse with the egg cell. Explain the sequence of events t…
• After fertilisation in a flowering plant, the zygote and the ovule undergo a series of changes. Trace the dev…
• Why is it essential for pollen to land on the stigma of a flower of the same species rather than just any sur…
• A flowering plant produces flowers that are functionally unisexual — bearing only pistils and no stamens. (a)…
• Both the ovule and the ovary undergo changes after fertilisation in a flowering plant. Distinguish between th…
• Distinguish between pollination and fertilisation in flowering plants on the basis of: (i) the structures inv…
• Testes in humans are located outside the abdominal cavity in the scrotum. Why is this positioning necessary f…
• A student says: 'The urethra in males is part of the excretory system, so it plays no role in reproduction.'…
• The male reproductive system includes accessory glands such as the seminal vesicles and prostate gland. Why a…
• Trace the journey of a sperm cell from where it is produced to where fertilisation occurs in the female body.…
• Explain any TWO distinct functions performed by the placenta during the development of the embryo in the uter…
• A fertilised egg implants in the uterine lining, which has become thick and richly supplied with blood. If th…
• Why does the uterus prepare its lining every month even before it is known whether fertilisation will occur?
• A copper-T placed in the uterus prevents pregnancy but does NOT protect against sexually transmitted infectio…
• Secondary sexual characters such as changed voice or new hair-growth patterns appear during puberty but are n…
• Both a surgical block of the vas deferens in the male and a surgical block of the fallopian tube in the femal…
• Sperm production in the testes requires a temperature lower than normal body temperature. How does the human…
• The sperms produced in the testes are not immediately capable of fertilising an egg on their own. Explain wha…
• A sperm must travel from the vagina all the way to the oviduct to fertilise an egg. Trace the path it takes,…
• The uterine lining thickens and becomes richly supplied with blood every month even before fertilisation has…
• The placenta plays a crucial role in the survival of the developing embryo. (i) Describe the structural featu…
• A girl notices that the uterine lining builds up each month but breaks down and is shed if no fertilisation o…
• A 14-year-old shows signs of early sexual maturation. Does this mean their reproductive system is fully devel…
• Why are condoms considered more useful than most other contraceptive methods for a person with multiple sexua…
• A couple relies solely on oral contraceptive pills for reproductive health protection. Evaluate whether this…
• Which of the following contraceptive methods works by preventing the release of eggs? (A) Copper-T (B) Condom…
• Blocking the vas deferens and blocking the fallopian tube both prevent fertilisation, yet they are fundamenta…
• Why can the copper-T cause side effects that a barrier method like a condom does not?
• In a region where sex-selective abortion of female foetuses is practised, what would be the long-term biologi…
• An adolescent girl is pressured by her family to marry and bear children before she has fully completed puber…
• Name any two bacterial and two viral sexually transmitted infections. For one of them, state a method that ca…
• Asexual reproduction produces offspring with very little genetic variation, yet it is widely used in nature.…
• [short_answer] Spore formation, vegetative propagation, and budding are structurally very different processes…
• In both flowering plants and human beings, fertilisation produces a zygote that must be nourished as it devel…
• A student argues: 'Since DNA copying already introduces small variations, there is no added advantage to sexu…
• [mcq] Sperms are produced in the testes, which are located in scrotal sacs outside the abdominal cavity. Whic…
• Trace the complete journey of a male gamete — from the moment it is produced in the human body to the moment…
• [long_answer] When fertilisation does not occur in a human female, the thickened uterine lining is shed as me…
• Copper-T and surgical blocking of the fallopian tube are both contraceptive methods used in females, but they…

Biology · Chapter 8: Heredity (77)

• Give one reason why offspring produced by sexual reproduction show more variation than those produced by asex…
• Which type of reproduction — asexual or sexual — produces greater variation among offspring, and why?
• What determines which variations in a population are preserved over generations, and how does this process af…
• In Mendel's cross between tall and short pea plants, all F1 plants were tall, but short plants reappeared in…
• A child has the same type of earlobe (free or attached) as one of their parents. What is the term used for th…
• When Mendel crossed tall and short pea plants, only tall plants appeared in the F1 generation. What does this…
• In Mendel's experiment, when F1 tall plants were self-pollinated, one quarter of the F2 offspring were short.…
• When Mendel's F1 tall round-seeded pea plants were self-pollinated, some F2 offspring showed combinations of…
• (a) Every sexually reproducing organism carries two copies of the gene for each trait. Why must each germ cel…
• Sexual reproduction generates far greater variation among offspring than asexual reproduction. (a) Explain wh…
• What is a gene?
• Using the example of plant height, explain how a gene controls a physical characteristic.
• Why does each germ cell carry only one copy of each gene? What would happen if germ cells had the same number…
• In an asexually reproducing bacterial population, trait A is present in 10% of individuals and trait B is pre…
• Population X reproduces only asexually for many generations, while Population Y of the same species reproduce…
• A sudden rise in environmental temperature kills most individuals in a species, but a small number survive an…
• How many pairs of chromosomes are present in a typical human cell? How many of these pairs are sex chromosome…
• A couple is expecting a baby. The mother contributes an X chromosome to the child. Explain how the father's c…
• In Mendel's dihybrid cross, F1 plants with round yellow seeds (RrYy) were self-pollinated. Among the F2 offsp…
• In a class, some students have free earlobes and some have attached earlobes. A student notices that both her…
• When Mendel crossed tall pea plants with short pea plants, all F1 progeny were tall. Yet when these F1 plants…
• [mcq] A pea plant has the genotype Tt. Which of the following best explains why it appears tall? (A) Both T a…
• Mendel observed no medium-height plants in the F1 generation when he crossed tall and short pea plants. Why d…
• In a dihybrid cross, an F1 plant with genotype RrYy is self-pollinated. Among the F2 seeds, new combinations…
• A pea plant true-breeding for tall stem (TT) is crossed with a true-breeding short plant (tt). In the F2 gene…
• Why must each germ cell carry only one copy of each gene, rather than two, for Mendel's laws of inheritance t…
• Two traits — seed shape (round R, wrinkled r) and seed colour (yellow Y, green y) — are controlled by genes o…
• [very_short_answer] In Mendel's monohybrid crosses, one parental trait disappeared in F1 but reappeared in on…
• A gene controls the production of an enzyme involved in making a growth hormone in pea plants. Explain, using…
• [long_answer] Mendel's law of independent assortment holds true only when the two genes considered are locate…
• A pea plant is tall because it produces a large amount of a particular growth hormone. Explain the chain of m…
• A mutant pea plant produces an enzyme involved in growth-hormone synthesis, but that enzyme functions at only…
• Why must each gamete (reproductive cell) carry only ONE copy of each gene, even though all other body cells c…
• In Mendel's dihybrid cross, two traits — seed shape and seed colour — are inherited independently. Explain wh…
• A student argues: 'If all genes were located on a single, continuous DNA strand with no division into chromos…
• During sexual reproduction, a child receives one chromosome from each pair from each parent. Explain how this…
• In human beings, females have XX chromosomes and males have XY chromosomes. Explain why the sex of a child is…
• A couple has four daughters. The father argues that it is the mother's genetics that keeps 'producing' girls.…
• In human beings, sex is determined by chromosomes inherited at the time of fertilisation, whereas in some org…
• A couple is expecting their fourth child. Their first three children are all girls. What is the probability t…
• A tall pea plant (TT) is crossed with a short pea plant (tt). All F1 plants are tall, and when F1 plants self…
• In a monohybrid cross between tall (Tt) and short (tt) pea plants, what is the expected ratio of tall to shor…
• Which of the following correctly explains why variations are important for a species? ((A)) Variations allow…
• A dihybrid cross between two pea plants with genotype RrYy × RrYy is performed. The F2 generation shows four…
• In sexually reproducing organisms, each germ cell carries only one copy of each gene. Why is this necessary?…
• The sex of a crocodile embryo is determined by the temperature at which fertilised eggs are incubated. This m…
• In a plant, shortness is controlled by a gene that produces a less efficient enzyme, resulting in lower hormo…
• In pea plants, two different traits such as seed colour and seed shape are inherited independently of each ot…
• In a population of bacteria reproducing asexually, a particular variation is found in 60% of individuals whil…
• Sexual reproduction generates more heritable variation than asexual reproduction primarily because: ((A)) Sex…
• Two pea plants, one with genotype TTWW (tall, violet flowers) and another with ttww (short, white flowers) ar…
• Assertion (A): In human beings, it is the father's chromosomal contribution that determines whether a child w…
• Assertion (A): Variants that are better suited to their environment survive and reproduce more successfully t…
• Assertion (A): Each body cell of a sexually reproducing organism has two copies of each chromosome. Reason (R…
• A child has blood group O. Her mother has blood group A and her father has blood group B. What does this tell…
• Why does a germ cell contain only one set of genes while all other body cells contain two sets?
• In pea plants, round seed shape (R) is dominant over wrinkled (r). A plant with round seeds is test-crossed w…
• In snails, an individual can change its sex during its lifetime. What does this indicate about the mechanism…
• Mendel crossed pea plants having tall stems and round seeds (TTRR) with plants having short stems and wrinkle…
• Explain how a gene controls a characteristic in an organism, using plant height as an example. Your answer sh…
• In a Mendelian monohybrid cross: (i) Why are there no plants of intermediate height (medium height) in the F1…
• With the help of a cross diagram, show the sex chromosome combinations possible in the offspring when a human…
• Asexual reproduction produces very little variation, while sexual reproduction produces considerably more. Ex…
• A pure-breeding pea plant with round yellow seeds (RRYY) is crossed with a pure-breeding plant with wrinkled…
• Mendel used garden pea plants to study heredity over two generations. (a) Mendel crossed a pure tall pea plan…
• Inheritance of sex in humans involves specific chromosomal mechanisms. (a) Describe the sex chromosome compos…
• The accumulation of heritable variations over generations drives diversity within a species. (a) Explain how…
• Read the following scenario and answer the questions: Anjali is studying inheritance of seed colour in peas,…
• Read the following and answer the questions: In a village, a farmer noticed that in his field of sugarcane, a…
• Read the following scenario and answer the questions: Rajat performed a genetics experiment with pea plants.…
• A population of bacteria reproduces asexually, while a population of pea plants reproduces sexually. Both pop…
• Mendel found that when F1 tall pea plants (Tt) self-pollinate, one-quarter of the F2 offspring are short. Yet…
• A student argues: 'Since sex in humans is genetically determined, and each chromosome pair provides one copy…
• Two traits of a pea plant — seed shape (round R / wrinkled r) and plant height (tall T / short t) — are locat…
• During the formation of germ cells in sexually reproducing organisms, one chromosome from each pair is includ…
• A plant hormone is produced by an enzyme encoded by gene T. Plants with genotype TT produce a large amount of…
• A tall pea plant with genotype TT is crossed with a short plant (tt) to produce F1 plants (Tt), which are all…

Physics · Chapter 10: The Human Eye and the Colourful World (80)

• What is the role of the crystalline lens in the human eye?
• What is the role of the ciliary muscles in enabling the eye to see both nearby and distant objects clearly?
• When you shift your gaze from a distant tree to a book held close to you, what change occurs in your eye lens…
• A person can read a newspaper held at arm's length but struggles to read the name board of a shop across the…
• A hypermetropic person cannot see nearby objects clearly. (i) Where does the image of a nearby object form in…
• What is presbyopia, and what structural changes in the eye cause it?
• A myopic eye has the image of a distant object forming in front of the retina instead of on it. State TWO pos…
• An elderly person uses bi-focal lenses. (i) What are bi-focal lenses? (ii) Describe the function of each port…
• When white light passes through a glass prism, the emergent ray does not travel in the same direction as the…
• What is the name given to the splitting of white light into its component colours when it passes through a gl…
• When white light passes through a glass prism and forms a spectrum, which colour bends the least and which be…
• Stars twinkle but planets do not. Why?
• Due to atmospheric refraction, does the Sun appear to rise earlier or later than it actually does? Give a rea…
• Why does the sky appear blue during the day?
• The cornea performs most of the refraction of light entering the eye, yet we still need the crystalline lens.…
• When you shift your gaze from a distant tree to a book held 25 cm away, describe what happens inside your eye…
• Most of the refraction of light entering the eye occurs at the cornea, yet it is the lens that allows us to s…
• When you shift your gaze from a distant tree to a book held 25 cm away, describe what happens to your ciliary…
• A person can read a billboard 50 m away with perfect clarity, but finds the text on her phone blurred when he…
• A myopic person can see objects clearly only up to 2 m. Which type of lens is used to correct this defect, an…
• Both myopia and hypermetropia involve the image not forming on the retina. How does the position of the image…
• A student can read the school notice board from across the room but struggles to read his textbook unless he…
• A person is unable to see distant objects clearly. State TWO possible structural reasons for this defect of v…
• An elderly person finds it difficult to read a newspaper but can see distant objects clearly without glasses.…
• How is presbyopia similar to hypermetropia in its symptoms, and yet different in its cause?
• A person suffers from both myopia and hypermetropia simultaneously. What type of spectacle lenses would be pr…
• The near point of a normal young adult is 25 cm, but for a hypermetropic person it is much farther. Explain w…
• Which of the following correctly describes the cause of myopia? (A) The eyeball is too short, causing the ima…
• A ray of white light enters a triangular glass prism through one refracting surface and exits through the oth…
• When light passes through a rectangular glass slab, the emergent ray is parallel to the incident ray. When li…
• In the refraction of light through a triangular glass prism, which of the following correctly describes the a…
• When white light passes through a glass prism, different colours deviate by different amounts. Using this obs…
• A student passes white light through a prism and sees a spectrum on a screen. She then passes just the red ba…
• Explain with a labelled ray diagram how a rainbow is formed in the sky after a rain shower. Name all the opti…
• A rainbow is always seen in the part of the sky that is opposite to the Sun. Which one of the following corre…
• Dispersion of white light occurs when it passes through a prism but NOT when it passes through a rectangular…
• A person can see nearby objects clearly but has difficulty seeing distant objects. Which type of lens is used…
• The part of the human eye that is responsible for most of the refraction of incoming light is the:
• When white light passes through a glass prism, the colour that deviates the LEAST is:
• The correct sequence of colours in the spectrum of white light from the least deviated to the most deviated i…
• Stars twinkle at night but planets do not. The most accurate reason for this difference is:
• A rainbow is always observed in the direction opposite to the Sun. Which set of optical phenomena is responsi…
• The sky appears dark to astronauts flying at very high altitudes because:
• In hypermetropia, the image of a nearby object is formed:
• Bifocal lenses are commonly prescribed for people suffering from:
• Which colour of light is scattered the MOST by fine particles in the earth's atmosphere?
• The Sun is visible to us about 2 minutes before actual sunrise. This is due to:
• The angle between the emergent ray and the direction of the incident ray when light passes through a prism is…
• The condition in which the crystalline lens of the eye becomes milky and cloudy, causing partial or complete…
• Assertion (A): Red light is used for danger signals at airports and on tall buildings. Reason (R): Red light…
• Assertion (A): When the ciliary muscles of the eye relax, the eye lens becomes thin and its focal length incr…
• Assertion (A): The apparent position of a star near the horizon is slightly higher than its actual position.…
• Assertion (A): White light passing through a second prism placed in an inverted position relative to the firs…
• Assertion (A): Objects seen through a column of hot air rising above a fire appear to waver. Reason (R): The…
• State two causes that can lead to the development of myopia in a human eye.
• What is the Tyndall effect? Give one example from nature where this phenomenon can be observed.
• Explain why the Sun appears reddish at sunrise and sunset but appears white or yellow-white at noon.
• What is the far point of a normal human eye? How does this differ in a person with myopia?
• The power of accommodation of a person's eye gradually decreases as they grow older. Name this condition and…
• Draw a labelled ray diagram showing how a concave lens corrects myopia in a person whose far point is closer…
• The human eye has several specialised parts that work together to form a clear image. Explain the specific fu…
• When white light is passed through a glass prism, a band of colours is observed on a screen placed on the oth…
• Explain why stars twinkle on a clear night. Your answer must include the role of the earth's atmosphere and t…
• A hypermetropic person has a near point of 1.5 m. Calculate the power of the corrective lens needed so that s…
• What is atmospheric refraction? How does it cause the apparent shift in the position of stars near the horizo…
• Differentiate between dispersion and scattering of light. How does the size of particles determine the colour…
• (a) With the help of a labelled ray diagram, explain the defect of hypermetropia, showing where the image is…
• (a) What is meant by the dispersion of white light? With the help of a labelled diagram, show how a glass pri…
• (a) Define the power of accommodation of the human eye. How do the ciliary muscles bring about this accommoda…
• Read the following and answer the questions that follow: Rahul, a Class 10 student, notices that when sunligh…
• Read the following and answer the questions that follow: Dr. Sharma, an ophthalmologist, examines three patie…
• Read the following and answer the questions that follow: Priya and her friends are on a stargazing trip on a…
• A star near the horizon appears to twinkle more vigorously than a star directly overhead. Using your knowledg…
• Why does the Sun appear to rise about 2 minutes before it actually crosses the horizon?
• Planets, unlike stars, do not appear to twinkle even though they are also very far away. Give a scientific re…
• A star near the horizon appears to be at a position slightly higher than its actual position in the sky. Usin…
• Why does the sky appear blue during the day, but an astronaut at very high altitude sees a dark sky instead?
• A beam of white light passes through a colloidal suspension containing very fine particles. A second colloida…
• When sunlight filters through a dense forest canopy containing mist, bright shafts of light become visible. E…
• A glass prism disperses white light into a spectrum of colours, but the eye's lens system does not produce ra…

Physics · Chapter 11: Electricity (30)

• What is an electric circuit?
• Define electric current. State its SI unit.
• In a metallic wire, electrons are the actual charge carriers, yet the conventional direction of electric curr…
• What is electric potential difference? State its SI unit and define it.
• State Ohm's law.
• In an electric circuit, the potential difference across a resistor is 12 V and the current through it is 3 A.…
• The resistance of a conductor is kept constant. If the potential difference across it is doubled, what happen…
• When the potential difference V across a conductor is plotted against the current I through it, a straight li…
• State the factors on which the resistance of a uniform metallic conductor depends.
• A nichrome wire of length l has a resistance R. It is replaced by another nichrome wire of the same cross-sec…
• Two wires are made of the same material and have the same length, but one is thicker than the other. Which wi…
• A student needs a wire with very high resistance for use in an electric heating device. She has two wires of…
• Three resistors of 4 Ω, 6 Ω, and 12 Ω are connected in parallel. Explain why the equivalent resistance of thi…
• An ammeter is connected at three different positions in a series circuit with three resistors: before the fir…
• Three resistors of 4 Ω, 6 Ω, and 10 Ω are connected in series. What is the equivalent resistance of the combi…
• A student connects a 2 Ω and an 8 Ω resistor in series to a 10 V battery. (a) Calculate the total resistance…
• A switch in a torch circuit is opened (turned off). Explain, in terms of what happens to the electric charges…
• [very_short_answer] Three resistors are connected in parallel across a battery of potential difference V. Wha…
• Three resistors of resistances R₁, R₂, and R₃ are connected in parallel. Write the expression for their equiv…
• [short_answer] Three resistors carrying currents I₁, I₂, and I₃ are connected in parallel across a battery. W…
• State TWO practical advantages of connecting electrical appliances in parallel rather than in series in a dom…
• State Joule's law of heating. Write the mathematical expression for heat produced in a resistor and explain w…
• Tungsten is preferred over most other metals for making the filament of an electric bulb. Which two propertie…
• Why is tungsten preferred over other metals for making the filaments of electric bulbs?
• In a metallic wire, electrons are the actual charge carriers, yet the conventional direction of electric curr…
• A charge of 180 C flows through a conductor in 2 minutes. (i) Calculate the electric current through the cond…
• An ammeter of very low resistance (nearly zero) is accidentally connected in parallel with a resistor of 10 Ω…
• Which of the following expressions correctly represents the electric power consumed in a circuit? (A) P = VI…
• A cell maintains a fixed potential difference across its terminals even when no current is drawn from it. (a)…
• A voltmeter connected across a resistor in a circuit reads 9 V, while an ammeter in series reads 3 A. (a) Cal…

Biology · Chapter 13: Our Environment (75)

• What term describes all the interacting organisms in an area together with the non-living physical factors of…
• A garden and a forest both contain living organisms interacting with their physical surroundings, yet one is…
• What is an ecosystem? Give one example of a biotic and one example of an abiotic component found in a pond ec…
• What role do decomposers play in an ecosystem, and what would happen to the environment if they were absent?
• Which of the following correctly explains why food chains rarely have more than four trophic levels? (A) Prod…
• A garden and a forest both contain living organisms interacting with physical factors. What makes one a natur…
• Which of the following best explains why decomposers are essential for the continuity of any ecosystem? (A) T…
• Only about 10% of the energy available at one trophic level is passed on to the next. Where does the remainin…
• A farmer uses pesticides on crops over many years. A hawk that hunts small mammals in those fields is found t…
• In a pond ecosystem, if all the decomposers were suddenly removed, the producers and consumers might initiall…
• A field ecologist studying a grassland notices that when a population of rabbits crashes due to disease, foxe…
• In the food chain Grass → Grasshopper → Frog → Snake, identify the trophic level occupied by each organism an…
• Only about 10% of the energy available at one trophic level passes on to the next. What happens to the remain…
• Which of the following correctly explains why harmful chemicals like pesticides are found in the highest conc…
• What is biological magnification? Name the organism in a food chain that would have the highest concentration…
• Only about 10% of the energy at one trophic level is available to the next level. Where does the remaining 90…
• A food chain in a grassland ecosystem is: Grass → Grasshopper → Frog → Snake → Hawk. If the grass captures 10…
• Food chains rarely extend beyond four trophic levels. Which of the following best explains this? (A) Producer…
• Explain the process of biological magnification. A non-degradable pesticide was detected at a concentration o…
• Energy flow through a food chain is described as unidirectional. What does this mean, and how is it different…
• A farmer sprays a non-degradable pesticide on a paddy field adjacent to a pond. Trace the pathway by which th…
• Green plants in a terrestrial ecosystem capture only about 1% of the sunlight that falls on their leaves. Con…
• A farmer sprays pesticides on crops near a pond. Trace the path by which these pesticides could reach a human…
• Define biodegradable and non-biodegradable substances. Give one example of each.
• Plastics do not decompose when buried in soil, even though many food materials do. Why are bacteria and other…
• Identify which of the following sets contains ONLY non-biodegradable items: (A) Vegetable peels, used tea lea…
• State two ways in which changes in modern lifestyle have led to increased generation of non-biodegradable was…
• Trace the step-by-step process by which UV radiation from the Sun leads to the formation of ozone in the uppe…
• CFCs were widely praised as safe, useful chemicals when they were first introduced. In light of what we now k…
• Which of the following correctly describes an ecosystem? (A) Only the living organisms in a habitat (B) All i…
• Which of the following is an example of a human-made (artificial) ecosystem? (A) Forest (B) Pond (C) Lake (D)…
• Approximately what percentage of the food eaten by an organism at one trophic level becomes available as body…
• Which of the following food chains is correctly ordered? (A) Goat → Grass → Human (B) Grass → Goat → Human (C…
• The progressive accumulation of non-degradable chemicals at each successive trophic level is called: (A) Biod…
• In which group do ALL items belong to non-biodegradable waste? (A) Vegetable peels, plastic bags, glass (B) P…
• The ozone layer protects life on Earth mainly by: (A) Providing oxygen for respiration (B) Shielding the Eart…
• Which class of synthetic chemicals is primarily responsible for the depletion of the ozone layer? (A) DDT (B)…
• Green plants in a terrestrial ecosystem capture approximately what percentage of the sunlight energy that fal…
• Which of the following best describes the flow of energy in an ecosystem? (A) Cyclic — energy keeps returning…
• [mcq] Which of the following contains ONLY biodegradable items? (A) Grass, flowers and leather (B) Grass, woo…
• When a series of branching food chains interconnect rather than forming a single straight line, the resulting…
• Improvements in lifestyle leading to increased use of disposable, non-biodegradable packaging has caused whic…
• [assertion_reason] Assertion (A): Among all organisms in a food chain, the highest concentration of pesticide…
• Assertion (A): Food chains in nature are generally limited to three or four trophic levels. Reason (R): A lar…
• Assertion (A): Ozone (O₃) found at higher levels of the atmosphere is beneficial, while at ground level it is…
• Define 'biodegradable substances'. Give one example each of a biodegradable and a non-biodegradable waste com…
• What are decomposers? Explain why an ecosystem cannot function normally in their absence.
• Pesticides sprayed on crops are not directly eaten by humans, yet they are detected in our food. Explain the…
• Distinguish between a food chain and a food web, giving one example of each.
• [short_answer] What are trophic levels? Using the food chain — Grass → Grasshopper → Frog → Snake → Eagle — i…
• Explain why the number of individuals at successive trophic levels in an ecosystem keeps decreasing. In a foo…
• What is biological magnification? Using a food chain as an example, explain why a carnivore at the top of the…
• [short_answer] Explain how ozone is formed naturally in the upper atmosphere. Name the group of chemicals mai…
• Suggest three environment-friendly practices that can help an individual reduce the amount of non-biodegradab…
• If all the organisms at one trophic level of an ecosystem are suddenly removed, what would be the consequence…
• [long_answer] (a) Define 'ecosystem'. Distinguish between biotic and abiotic components, giving two examples…
• (a) What is the ozone layer and where is it found in the atmosphere? (b) Describe how UV radiation leads to t…
• (a) Distinguish between biodegradable and non-biodegradable substances with two examples each. (b) How do non…
• Read the following passage and answer the questions that follow: A farmer applied large quantities of pestici…
• Read the following and answer the questions that follow: A class was asked to bury two sets of waste material…
• Read the following and answer the questions that follow: In a grassland ecosystem, the following food chain e…
• Why can bacteria and fungi not break down plastics in the environment, even though they can break down food a…
• A student buries two pits in the school garden — one with vegetable peels and spoilt food, and another with p…
• Which of the following best explains why improvements in lifestyle and changes in packaging together pose a g…
• Distinguish between biodegradable and non-biodegradable substances with one example each. Describe one specif…
• A town switches entirely to biodegradable packaging and stops using plastics. A student argues that this mean…
• The introduction of disposable plastic cups in trains was initially welcomed for hygiene reasons, yet it crea…
• A non-biodegradable substance is sometimes described as 'environmentally inert.' Under what conditions might…
• What is the role of decomposers in managing natural waste, and why does their absence create a problem that h…
• Trace the journey of a pesticide molecule from a farmer's field all the way to a human body, explaining the r…
• The energy available at each trophic level decreases, yet harmful chemicals like pesticides increase in conce…
• Green plants capture only about 1% of the sunlight falling on them, and only about 10% of energy at any troph…
• Decomposers play a vital role in sustaining the productivity of green plants in an ecosystem. Separately, the…
• Consider a simple food chain: Grass → Grasshopper → Frog → Snake → Hawk. (i) At which trophic level would bio…
• Modern lifestyle changes and new packaging practices have led to a significant rise in non-biodegradable wast…